Grid controlled mercury arc circuit controller



Jan. 24, 1933. w, LYLE 1,894,994

GRID CONTROLLED MERCURY ARC CIRCUIT CONTROLLER Filed Nov. 27. 1929 Hy. Z. 3 2

26 2 39 v :E-23 l qlrfl 24 INVENTOR fidQr/q n4 Ly/e.

ATTORNEY Patented Jan. 24, 19 33 UNITED STATES PATENT OFFICE FREDERICK W. LYLE, OF WILKINSB'URG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA GRID CONTROLLED MERCURY ARC CIRCUIT CONTROLLER Application filed November 27, 1929. Serial No. 410,092.

My invention relates to current control means-for controlling electric currents, and particularly to control means for electric motors of the reciprocating type.

One object of my invention is to provide means for causing a reciprocating motion to be imparted to the armature of an electric motor by making and breaking a current through a winding of the motor at appropriate intervals.

Another objectof my invention is to provide means for interrupting the flow of relatively large currents at relatively frequent intervals without arcing at separable electrical contacts.

Another object of my invention is to provide means for interrupting heavy electric currents, and currents flowin through highly inductive circuits, without the arcing which ordinarily takes place where separa le contacts are opened under load in such circuits.

A further object of my invention is to provide means for making-and breaking heav electric currents at frequent intervals wit apparatus which is not subject to the deterioration produced by arcing at separable contacts.

Other objects of my invention will become apparent on reading the following description taken in conjunction with the drawing, in which Figure 1 shows schematicall a reci rocating electric motor provided with a grid-controlled mercury-arc device and embodying the principles of my invention, and

Fig. 2 shows an arrangement for controlling the making and breaking of the motor circuit in response to the magnitude of the current drawn by the motor.

Reciprocating electric motors, adapted to cause a rapid reciprocation of a movable member, have previously been roposed for use in electric hammers pile drivers and apparatus of similar kin s. Many such electric motors are designed to be operated by causing a heavy current to flow throng windings which actuate a movable armature member and cause a rectilinear movement.

thereof in one direction. The current is then interrupted in these windings, and in some cases caused to start flowing through other windings, thereby permitting the armature to be moved in the opposite direction toward its initial position, where it is arranged to strike a blow upon the pile or other object which the hammer is intended to drive. Where such reciprocating motors are designed for heavy duty, it is necessary to make and break at very frequent intervals electric currents of several hundred amperes. The repeated interruption of such large currents at fre uent intervals has hitherto presented a pro lem for wbliich no successful solution has been availa e.

In accordance with the principles of iny invention, I control the fiow of current from an alternating current source through the operative windings of a reciprocating motor of the type above described through the agency of a grid-controlled gaseous discharge device. A mercury arc in vacuum is a convenient form of such a discharge device, although my invention is not limited to gas- (teous discharge devices of this particular As is well known, the flow of current in high vacuum electrical dischar e devices provi ed with hot cathodes may be interrupted by imposing a negative charge upon a control 0 ectrode positioned between the anode and cathode. Such devices, however, suffer from the limitation that it is impossible, with cathodes of )ractical dimensions, to obtain currents of tie magnitude suitable for the operation of electric meters of large power. On the other hand, gaseous discharge devices, particularly those of-the m'ercury are type are capable of carryin currents of sufficlent magnitude, but when it is attempted to interrupt current flow in such devices by imposing a negative charge on control electrodes, it is found that current flow continues substantially unaffected. It is, however, found that once the current in a gaesous discharge device has been caused to fall to zero by some external a ency, a negative charge imparted to the gri -will prevent the resumption of current flow therein. It is, according- 1y, ossible by supplying current through'a gri -controlled gaseous discharge device from an alternating current source to electrical power a paratus, to cause an effective interruption 0? current flow at the end of any half cycle of the alternating current by making a control electrode negative in potential re ative to the cathode; and conversely to initiate flow of current at; any desired instant by making the control electrode positive in potential relative to the cathode. By employing gaseous discharge arrangements, of which the ordinary form of full wave mercury are rectifier is an example, which permit the flow of both half waves of alternating current to a load, it is possible to supply current continuously through any desired number of half periods of the alternating current source, and likewise, to interrupt it through any desired number of half periods of the alternating current source; and hence for practical purposes to initiate and interrupt the flow of heavy load currents for any desired intervals oftime. Since such arrangements employno se )arable contacts which are required to open w ile carrying the ower current, no dillieulties are experienced rom arcing and deterioration such as is characteristic of ordinary mechanical switching devices.

With the foregoing principles and objects of invention in mind, reference is made to the accompanying drawing, in which the reference numeral 1 designates the windings on the stator of a reciprocating motor of a t pe too well known in the art to require detalled description. The flow of current from an alternating current source 2 through the windings 1 produces a flux in the magnetic circuit of the reciprocating motor and attracts a movable armature 3 which may be mechanically interlinked with a hammer or other device, to which it is desired to impart reci rocating motion. Current through the win ings 1 flowsto a control aggregate 4 comprising an inductance 5 connected in shunt across the anodes of a mercury arc tube 6 having main anodes 7, control electrodes 8, and a mercury cathode 9 kept continuously excited by a side branch 11. The cathode 9 is connected with the mid point 12 of the inductance 5. The two control electrodes 8 may be connected together to the hinge terminal of a double throw switch 13. One of the cooperating terminals 14 of the switch 13 may be connected to the positive terminal of a source of electromotive force 15, the negative terminal of which is connected to the cathode 9. The other cooperating terminal of the switch 13 is connected to the negative terminal'of another source of electromotive force 16, the positive terminal of which is connected to the cathode 9. The switch'13 is mechanically interlinked with the reciprocating armature '3 through a lost-motion connection 17 so that when the latter is in its-righthand posicontrol electrodes negative in potential relative to the cathode.

The mode of operation of the above-dcscribed arrangement is as follows:

Current fiowsfrom the side of the alternating current source 2 which happens to be positive to the adjacent anode of the mercury are 6. If the armature 3 is in its right position the control grids 8 have a positive potential relative to the cathode 9 and hence I current flows through the mercury are 6 to the cathode 9, back to the neutral point 12 of the inductance, and through one half of the latter to the other portion of the winding 1 and its adjacent side of the alternating current source 2. WVhen the polarity of'the alternating current source 2 reverses, current flow ceases from the rectifier anode from which it has previously been flowing and starts to flow from'the opposite anode to the cathode 9; thcnee;'to the neutral 12 of the inductance 5, the opposite half of the wind-- ings of the latter,-and back to the other side of the alternating current source 2. Current flow thus continues from one anode of the mercury arc tube 6 as long as the control electrodes 8 are positive relative to the cathode 9. The armature 3 is, accordingly, drawn to the left and the lost motion connection 17 permits this movement to continue until, as the armature 3 nears the end of its stroke, the switch 13 is reversed and caused to make the control grids 8 negative in potential relative to the cathode 9. At the end of the next succeeding half cycle of alternating current -from the source 2, current flow cannot start through either arm of the rectifier 6 and current flow through the windings 1 remains interrupted. The force of a tension spring, or if desired any other biasing means as the force of gravity, then causes the armature 3 to move to the right toward its initial position, where it imparts a blow to the hammer or other device which it is required to actuate. Because of the lostmotion connection 17 the switch 13 remains in the condition last described until the armature 3 approaches the right end of its stroke; switch 13 is then moved to again make the control electrodes 8 positive relative to the cathode; current flow can then resume from the alternating current source 2 through the windings 1 and one anode of the mercury arc tube 6; the hammer'3 is again drawn to that lleft, and this cycle repeats itself indefin1 e y.

Since the switch 13 merely controls the potential of control electrodes 8, it is not required to interrint any substantial current and no ditlicuities from arcing at its terminals are experienced.

Instead of the mechanically actuated switch 13 andsources 15 and 16, other means may be employed to impart the desired potentials to the control electrodes 8. Thus, in general, the magnitude of the current drawn from the source 2 by the motor will vary with the position of the armature 3, the current being greater, let us say, when the armature 3 is atthe ri ht end of its stroke than when it is at the left end. Figure 2 shows an arrangement for utilizing this fact to cause interruption of the motor current at proper times. A gaseous discharge device 6 is utilized to short-circuit a portion of an auto-transformer 5 in series with the windings 1 when the current is to be increased through these windings. This gaseous discharge device 6 has two anodes 7, a mercury pool cathode 9, two grids 8 interposed between the cathode 9 and the respective anodes 7, and a keep-alive circuit 11.

The anodes 7 are connected at or near opposite ends of the auto transformer 5. The cathode 9 is connected to the midpoint 12 of the auto transformer 5. A battery 24 and I the circuitof a full wave rectifier 21 are utilized to establish the desired bias on the grids 8. l

The anodes 'of the rectifier 21 are connected in series with the secondary of the transformer 22 whose primary is in series with the windings 1 and the source 2. These anodes are also shunted by the transformer 29.

The cathode of the rectifier 21 is connected to the positive pole of the battery 21 whose negative pole is connected to the grids 8. A resistor 23 is connected between the connections to the grids 8 and the cathode 9 and the return circuit to the midpoint 30 of the transformer 29.

The circuit of the rectifier 21 and the battery 24 oppose each other in respect to the potential to be placed on the grids 8. When the armature 3 is in its left hand position, the current established in the secondary of the transformer 22 will pass through the rectifier 21 and overcome the op osition of the battery 24. Accordingly, t e grids 8 will have a ositive potential with respect to the cathode iiecause of the voltage drop across the resistor 23. The gaseous discharge device will then be conducting.

When the.device 6 is conducting a portion of the auto transformer is short circuited. If the current enters the left-hand side of the transformer 5, it passes to the left-hand anode of device 6 through the tube to the cathode 9 and then to the midpoint 12 of the transformer 5, thus short-circuitin the lefthand portion of the transformer. f the current wave is in the opposite direction, the right-hand portion of the auto transformer 5 is short circuited.

As the armature 3 is drawn to the right into the winding 1, the increased inductance cuts down the current with the result that the current induced in the rectifier 21 through the transformer 22 no longer redominates over the battery 24. The gri s 8 become negative with respect to the cathode and, accordingly, the discharge through the discharge device 6 ceases when the potential of the wave approaches or passes through zero.

With the stopping of the discharge through the device 6, the armature 3 moves to its extreme left hand position. With the elimination of the inductance effect on the winding 1, the current is again increased in the circuit of rectifier 21, the 0 position of battery 24 is overcome and the tu e 6 is again made conducting by the positive potential on the grids 8 with respect to the cathode 9.

Phase displacing means such as condenser 25 may be connected with rectifier 21 to insure that the phase of the electromotive force applied to'control electrodes 8 is properly related to the alternating electromotive force at the terminals of rectifier 6. Also, an inductance 26 may be inserted in the rectified current circuit of rectifier 21. Condenser 27 may be connected across the terminals of resistor 23 and resistor 28 may be connected in series with'rectifier 21 to insure proper timing of the electromotive force applied to control electrodes 8.

It will be evident that the potential applied to electrodes 8 may alternatively be controlled by a suitable relay responsive to large current in windings 1 to impart a positive potential to control electrodes 8 and to small current in said windings to impart a negative potential thereto, and this relay may be provided with suitable time delay devices to lag the application of the negative potential aforesaid with respect to the decreased value of motor current.

While I have described specific circuit connections, it will be recognized that other circuit connections may readily be devised, the principal requirement being an arrangement by means of which one-half wave of alternating current may flow from one anode, and the other half wave of alternating current may fiow from another anode. Alternative arrangements which permit the performance of such functions are well known in the art; for example, the electrical discharge device (i and transformer 5 may be connected in series with the alternating current line at any point in the circuit and need not intervene between two halves of the winding 1 of the motor in the manner shown in Figure 1. It will also be recognized that the windings 1 of the motor are not necessarily separate from each other in physical position but may 5 be composed of alternate coils sandwiched beload.

'tially the midpoint of said inductance and In accordance with the patent statutes, I have described a particular embodiment of my invention, but it will be evident to those skilled in the art that the principles thereof are of broader application and many different ways of embodying them will be readily apparent. I, accordingly, desire that the following claims shall be given the broadest interpretation of which their terms are susceptible in view of the limitations imposed by the prior art.

I claim as my invention:

1. In combination, a reciprocating electric motor having windings, an inductance in series with said windings and a gaseous discharge device in circuit with said inductance, said gaseous discharge device having anodes connected to opposite portions of said inductance and a cathode connected to substanmeans to short circuit a portion of said inductance by said gaseous discharge device in response to the movement of said motor.

2. In combination with an electric motor having windings, an inductance in series with said windings and an electric discharge device in circuit with said inductance, said electric discharge device having anodes con- 4 nected to opposite portions of said inductance and a cathode connected to substantially the midpoint of said inductance, electrodes for controlling current flow in said discharge device, and means for controlling the otential of said controlling electrodes re ative to said cathode.

3. In combination with an induction motor having windings, an inductance in series with said windings and an electric dischar e device in circuit with said inductance, sai electric discharge device having anodes connected to opposite portions of said inductance and a cathode connected to substantially the midpoint of said inductance, electrodes for controlling current flow in said discharge device and means for controlling the potential '0 said controlling electrodes relative to said cathode.

4. In combination with an electric apparatus having primary windings and secondary windings, an inductance in series with said primary windings and an electric discharge device in circuit with said inductance, said electric discharge device having anodes connected to opposite portions of said inductance and a cathode connected to substantially the midpoint of said inductance, electrodes for controlling current flow in said discharge device, and means for controlling the potential of said controlling electrodes relative to said cathode.

5. In combination with an electric apparatus re uiring alternating current and having wincings, an inductance in series with said windings and an electric dischar e device in circuit with said inductance, said electric discharge device having anodes connected to opposite portions of said inductance and a cathode connected to substantially the midpoint of said inductance, electrodes for controlling current flow in said discharge device, and means for controlling the potential of said controlling electrodes relative to said cathode.

6. In combination with an electrical load, a transformer having primary turns in series with said lead, an electrical discharge device comprising a pair of electrodes of one polarity and one electrode of the opposite polarity and means for controlling current flow therebetween, said pair of electrodes being connected directly to two ,oints spaced apart on secondary turns of sai transformer and said one electrode being connected directly' to a point on said secondary substantially midway between said two points.

'7. In combination with an electrical load, a primary winding of a transformer connected in series with said load, a full-wave rectifier having one terminal of one polarity and a pair of terminals of the opposite polarity and means for controlling current flow therebetween, said pair of terminals being connected directly to two points spaced apart on secondary turns of said transformer and said one terminalbeing connected directly to a point substantially midway between said two points on said secondary.

In testimony whereof. I have hereunto subscribed my name this 22nd day of Novem- FREDERICK W. LYLE.

. ber, 1929.

uzn'e'dam'mzn 1,894,994.Fl'edericli WiI/ylc, Psi CoN'monnnn Msncrmr'Aiic Omcurr Cournomnn. Pate t atedpJanuar-y 24 1933. i Disclaimer filed Boecember 24, 1934, by the aesignee, Westinghouse &-Man 1 afacturi1ig Hereb enters this disclaimer to that part of the claim in said specification which ismthefo owingwordstowitr" LeYour petitioner hereby disclaims the subject matter of claims 2 3, and 4 except where said anode connections are to points intermediate the ends of said :nductanoe.'

2. Your petitioner hereby disclaims the subject matter of claim 5 except where the potential of the controlling electrodes relative to the cathode var es recurrently at a fre uency independent of that of thealternating current recited.

' 3. our petitioner hereby disclaimsthe subject matter of claim 6 except for arrangements in which the current controlling means acts to produce recurrent variations of the current flow in said transformer -at relatively frequent intervals.

different-from the periods of the voltage su ply for the transformer primary.

4. Your getitioner hereby disclaims t 'e subject" matter of claim 7, except for electrical disc to substantially ecrease the efi'ect .of space charge in impeding current flow between the recited electrodes of opposite olanty.

[Qflicial Gazette January 15, 936.1

e devices which contain a suificient pressure of gaseous-atmosphere 

